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Mimosa pudica

Mimosa pudica (Sensitive Plant) (pudica = shy), is a creeping annual or perennial herb often grown for its curiosity value: the compound leaves fold inward and droop when touched, re-opening within minutes. The species is native to South America and Central America, but is now a pantropical weed.

Description

The stem is erect in young plants, but becomes creeping or trailing with age. The stem is slender, branching, and sparsely to densely prickly, growing to a length of 1.5 m (5 ft). The leaves are bipinnately compound, with one or two pinnae pairs, and 10-26 leaflets per pinna. The petioles are also prickly. Pedunculate (stalked) pale pink or purple flower heads arise from the leaf axils. The globose to ovoid heads are 8-10 mm in diameter (excluding the stamens). On close examination, it is seen that the floret petals are red in their upper part and the filaments are pink to lavender. The fruit consists of clusters of 2-8 pods from 1-2 cm long each, these prickly on the margins. The pods break into 2-5 segments and contain pale brown seeds some 2.5 mm long. The flowers are pollinated by the wind and insects.

Plant movement

Mimosa pudica is well known for its rapid plant movement. In the evening the leaflets will fold together and the whole leaf droops downward. It then re-opens at sunrise. This type of motion has been termed nyctinastic movement. The leaves also close up under various other stimuli, such as touching, warming, or shaking. The stimulus can also be transmitted to neighbouring leaves. These types of movements have been termed seismonastic movements. The movement is caused by "a rapid loss of pressure in strategically situated cells that cause the leaves to droop right before one’s eyes". This characteristic is quite common within the Mimosaceae family..

Taxonomy and nomenclature

Mimosa pendula was first formally described by Carl Linnaeus in Species Plantarum in 1753. The species epithet, pudica, is Latin for "bashful" or "shrinking", alluding to its shrinking reaction to contact.

Common names

The species is known by numerous common names including

sensitive plant
humble plant
shameplant
sleeping grass
touch-me-not.

The Chinese name for this plant 含羞草 translates to "shyness grass". Its Sinhala name is Nidikumba, where 'nidi' means 'sleep'. Its Tamil name is Thottal Sinungi, where 'Thottal' means 'touched' and 'Sinungi' means 'little cry'. Other non-English common names include Makahiya (Philippines, with maka- meaning "quite" or "tendency to be", and -hiya meaning "shy", or "shyness"), Mori Vivi (West Indies), and mate-loi (false death) (Tonga).

Distribution

The species is native to South America and Central America. It has been introduced to many other regions and is regarded as an invasive species in Tanzania, South Asia and South East Asia and many Pacific Islands . It is also regarded as invasive in parts of Australia. It is a declared weed in the Northern Territory, a declared plant in Western Australia, although not naturalised there, and control is recommended in Queensland.

The species has also been introduced to Nigeria, Seychelles, Mauritius and East Asia but is not regarded as invasive in those places.

Agricultural impacts

The species can be a troublesome weed in tropical crops, particularly when fields are hand cultivated. Dry thickets may become a fire hazard. In some cases it has become a forage plant although the variety in Hawaii is reported to be toxic to livestock.

Cultivation

In cultivation, this plant is most often grown as an indoor annual, but is also grown for groundcover. Propagation is generally by seed.

Uses

Mimosa pudica is sold as an educational product and novelty gift sometimes under the trademark name TickleMe Plant.

Medicinal properties

The plant lajjalu described in Ayurveda has been identified as Mimosa pudica. This plant has several alternate Sanskrit common names, including Namaskari, and Rakta Paadi.

In Ayurveda, the plant is described as a plant which folds itself when touched and spreads its leaves once again after a while. It is said to have a bitter and astringent taste, and has a history of use for the treatment of various ailments. Most commonly used is the root, but leaves, flowers, bark, and fruit can also be implemented.

A list of some of the notable chemical compounds found in Mimosa pudica can be found here: